1. Field of the Invention
The present invention relates to information handling systems and more particularly to information handling systems in which method and apparatus are employed to clip fixed character strings against a viewport in a graphics display system.
2. Description of the Prior Art
The following are systems representative of the prior art.
"Fundamentals of Interactive Computer Graphics" by Foley and Van Dam, published by Addison, Wesley Publishing Company, 1982 at pages 152-153 and pages 484-485, discusses generally several techniques for clipping fixed character strings agains a viewport.
More specifically FIGS. 4.10, 4.11, 4.12, show three situations for clipping fixed character strings against the clipping window.
Although the Foley and Van Dam text generally discusses the problem of clipping fixed character strings in a raster graphics display system, the text does not teach nor suggest the implementation as described and claimed herein according to the present invention.
Bresenham in a article entitled "Algorithm for Computer Control of Digital Plotter", IBM System Journal, Vol. 4 Number 1, 1965, at pages 25-30, describes the basic line generating algorithm which is employed in most graphics display systems.
However, the article does not teach the method for transforming and clipping fixed character strings in accordance with the present invention.
Characters for display on a graphics display system can be represented as programmed characters comprised of individual graphic primitives (lines, points, etc.) or as fixed characters which contain a fixed pattern of picture elements (pels) defining that character. Fixed characters are typically defined in terms of the resultant character display size. This creates a problem when a character string to be displayed by a program must be clipped so that it will fit within a viewport or the display monitor. In the prior art, the character string was first mapped from device independent (world) coordinates to display monitor coordinates and then clipping against the viewport window was formed. This frequently led to problems when the device independent coordinates could not be mapped to the display monitor coordinates resulting in a coordinate overflow and error condition.